Types of Electrical Wire For Different Wiring Applications, Romex Cable
Electrical wire and cable is a high quantity item in the wire and cable field. This article discusses the THHN single conductor electrical wire, Romex and UF-B Cable (underground cable). Electrical wire can be used indoors or outdoors. Romex is only an indoor cable because the jacket doesn’t have the ability to resist rain, moisture and solvents.
Nowadays THHN is always dual rated THHN and THWN. A lot of electricians require the THWN for a specific job and the cost of adding that approval is minimal so it always has the dual rating. THHN wire is a 600 Volt PVC (Polyvinyl chloride) wire with a nylon coating for easy installation into conduit or tray. It’s rated for 90°C and has UL approvals. It’s made from soft drawn bare copper with only 19 copper strands to make sure it’s stiff enough to push easily by conduit or tray.
Romex Wire is very similar because it’s the THHN/THWN conductors with an over all PVC jacket so that you can send 2-3 conductors with a ground wire by conduit at once. Romex wire is only used indoors though, so if you need an outdoor / underground cable then you should see the UF-B Cable. It has a better jacket to resist anything outdoors. The cost difference isn’t that high when upgrading to UF-B so it’s well worth it to make sure you’re using the correct cable. Sometimes people will run Romex outdoors for a few feet but it definitely isn’t worth it in the long run.